Sex-Related Pronotal Differentiation and Allometry in Dorcadion boluense corallinum (Coleoptera: Cerambycidae)

Sex-related variation in pronotal form was examined in a Kızılcahamam population of Dorcadion boluense corallinum using landmark-based geometric morphometrics. A total of 80 adults, comprising 30 females and 50 males, were examined using standardized dorsal images of the pronotum. Eight fixed homologous landmarks were digitized. Sexual size dimorphism was evaluated using centroid size, whereas symmetric pronotal shape variation was analyzed through principal component analysis, Procrustes linear models, discriminant function analysis, and morphological disparity comparisons. Females had significantly greater pronotal centroid size than males, with a mean difference of 8.7% and a large effect size. Sex explained 76.79% of symmetric pronotal shape variation. Females showed a broader and more compact pronotum, whereas males exhibited a narrower and more elongate configuration. Although centroid size was significantly associated with shape in the overall regression, this relationship was no longer significant after sex was included in the model, and no difference in allometric slopes was detected between the sexes. Discriminant analysis achieved 100% classification accuracy under leave-one-out cross-validation, while within-sex Procrustes variance did not differ significantly. These findings demonstrate pronounced sexual dimorphism in pronotal size and shape and indicate that the observed shape differentiation primarily reflects sex rather than an independent allometric effect. The results also support the explicit consideration of sex in comparative morphometric studies of Dorcadion.